Re: x-post: Bike Biz: Wheel ejection theory goes legal



J

Joe Riel

Guest
jim beam <[email protected]> writes:

> Tim McNamara wrote:
> <snip>
>> FWIW my logic goes:
>> A. A disk brake can cause an ejection force on the front wheel.
>> B. There is no need for an ejection force, as forks can easily be
>> designed to eliminate it.
>> C. Forks should be redesigned to eliminate the ejection force.
>> The background assumption, of course, is that wheel ejection is a
>> bad thing and is to be avoided.

>
> the logical flaw is amazing. illustration:
>
> 1. use of a bridge causes a collapsing force on it.
> 2. there is no need for a collapsing force.
> 3. bridges should not be used.


> the real consideration of course is how great the collapsing force is
> in relation to capacity, not whether a collapsing force exists.
> repeated failure to recognize that fundamental point is a truly
> extraordinary mental block.


Suppose the bridge were designed so that the entire structure depended
on the clamping of a quick-release to hold it together. Traffic on
the bridge would apply a force to the QR that tended to eject it,
however, if clamped with the "speced" tightness, the serrations in the
faces would provide a 3x margin to the rated load of the bridge.
Assume the QR was inspected regularly by a trained operator and access
by others was not an issue. Would anyone consider that a reasonable
design? What if the operator had the training and dedication of a
typical mountain bike rider (with respect to the proper operation of
QRs)?


--
Joe Riel
 
On Feb 13, 4:31 pm, Ben C <[email protected]> wrote:
>
>
> I think jim beam's point was that this was a tensile fatigue cycle,
> which tends to be worse than a compressive one, especially for things
> that are cast.


That was jim beam's point, although he takes the phrase "tends to be
worse" and translates it to "YOU MUST NEVER USE CASTINGS IN TENSILE
FATIGUE, IDIOT!!" or something like that. ;-)

There are several things you should realize about this. First,
tension (i.e. tensile fatigue) stresses are present in anything that
undergoes repeated bending. The tension happens on the outside of the
bend.

Second, tension (i.e. tensile fatigue) happens in anything that
undergoes repeated twisting, or torque. In that case, the tension
tends to be directed at a 45 degree angle to the torque axis.

Those two concepts are basic engineering mechanics. You can
demonstrate them easily, by bending and twisting a rubber eraser.
Putting it all together, you should be able to understand that your
cranks, stem, brake levers, brake arms, seatpost, shift levers,
handlebars, etc. all undergo tensile fatigue. It's possible to
successfully design for it.

But third (and perhaps easiest to understand) is that the specific
thing jim beam warns about - front mounting of disk brakes - has been
employed on multi-hundred-pound motorcycles for many decades. The
direct tensile stresses that come from such mounting are small, and
very easily accommodated. If they were not, NHTSA and CPSC would have
told you about it in the recall documents for those motorcycles.

So yes, there's a grain of metallurgical truth in what j.b. says. But
the design proclamations he derives from it are nonsense. He's making
a mountain out of a molehill for reasons of his own.

- Frank Krygowski
 
On Feb 13, 11:19 pm, Michael Press <[email protected]> wrote:
> In article
> <[email protected]>,
>
>
>
>
>
> [email protected] wrote:
> > On Mon, 12 Feb 2007 23:05:05 -0700, [email protected] wrote:

>
> > [snip]

>
> > >You may not like such questions, but they're the ones that any lawyer
> > >or expert trying to reconstruct an accident would ask. Whatever Jobst
> > >may think about the principles, here's his timely comment in another
> > >current thread on plaintiffs and accident reconstruction:

>
> > >"I would like to have seen the bicycle [another bike, not Missy's]
> > >right after the incident. It has been my experience that
> > >reconstruction of what occurred is often easier than first
> > >indications. That has been so, in every case in which I was called to
> > >testify. That is to say, the event did not occur as plaintiff
> > >described."

>
> > [snip]

>
> > Woe is me! I thought that I included the link to Jobst's post, but I
> > didn't. Here it is:

>
> >http://groups.google.com/group/rec.bicycles.tech/msg/af73416d9e457b72

>
> Can we get the thread tree display from gg?
>
> --
> Michael Press


Dear Michael,

Yes, you can get the thread-tree display from Google Groups for a link
like this to an individual message:

http://groups.google.com/group/rec.bicycles.tech/msg/af73416d9e457b72

Near the top of an individual-message page will be a heading "Message
from discussion whatever-the-thread-title-is"

In this case, it's "Message from Custom fork- wheel ejection risk?"

Click on the topic, and you'll go to the thread itself from the
individual message:

http://groups.google.com/group/rec....7b73c517e9/af73416d9e457b72?#af73416d9e457b72

The advantages of an individual-message link is that it's shorter and
goes directly to the messsage. Just using Google Groups search will
only get you to the 10-post section of a thread that contains the
target, not to the exact post.

So I find a post with the search function, but then use the shorter,
direct link to the target (found under "more options" as "individual
post"), but I forget that posters unfamiliar with Google Groups can
easily get lost in the latest incarnation of what used to be an easier-
to-navigate site.

Whether you see a tree on the left of a full-thread display depends on
what Google Group settings you choose under "more options" near the
top, which lets you pick fixed or proportional text and whether to
hide or display the "message list."

In large threads, it can be tricky to find new posts. I usually sort
the message-list/thread-tree by date and then grovel around at the
bottom.

Cheers,

Carl Fogel
 
J

jim beam

Guest
[email protected] wrote:
> On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:
>> EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
>> Pinder, and I doubt they'll trust anyone else who claims they checked their
>> QRs before the QRs magically loosen.

>
> I think this is true, with the possible exception of CF (who seems to
> sit back and sling questions, but seldom states an actual opinion).
>
> EP and jb go on about initial conditions not being verified (or some
> such thing) without ever specifying what they'd accept as a standard
> for verification. Obviously, the procedures normally used (such as
> clamp angle of the QR) don't qualify in their eyes.
>
> They give the impression the only accepted testimony involves QRs
> tightened with a torque wrench whose resolution is 0.1 inch-pounds.
> Then checked again at the bottom of a suitable descent. With the
> entire process done in front of three witnesses. Who sign a document
> of testimony. Which is notarized.


classic krygowski getting red herringed. torque wrench means nothing
across different qr's since friction on each is different. all that
matters is indention, since that's what generates retention force.

>
> I think everyone accepts that most QRs hold most front disk axles in
> place most of the time. IOW, the set of conditions generating
> loosening and ejection is uncommon, and some of the conditions may not
> be known.


"may not be known"??? because that's the only way to create a problem -
resort to saying that something "may not be known" because everything
else is shown to be alarmist drivel? how many dragons are under my desk
frank? want to scare the kiddies with them too? idiot.

> It's foolish to expect a stellar verification team to
> happen to be present at the top of a particular hill just before all
> conditions are right to cause loosening or ejection.
>
> Unless, that is, someone purposely sets up a demonstration just to
> convince them. But to go through that trouble, one would have to
> pretend their opinions actually mattered, and the concensus here seems
> to disagree.


the consensus of those studiously avoiding the math... idiot.
 
J

jim beam

Guest
[email protected] wrote:
> On Feb 13, 4:31 pm, Ben C <[email protected]> wrote:
>>
>> I think jim beam's point was that this was a tensile fatigue cycle,
>> which tends to be worse than a compressive one, especially for things
>> that are cast.

>
> That was jim beam's point, although he takes the phrase "tends to be
> worse" and translates it to "YOU MUST NEVER USE CASTINGS IN TENSILE
> FATIGUE, IDIOT!!" or something like that. ;-)


idiot.

>
> There are several things you should realize about this. First,
> tension (i.e. tensile fatigue) stresses are present in anything that
> undergoes repeated bending. The tension happens on the outside of the
> bend.


oh, this is just too stupid... think about what you've just written.
idiot.

>
> Second, tension (i.e. tensile fatigue) happens in anything that
> undergoes repeated twisting, or torque. In that case, the tension
> tends to be directed at a 45 degree angle to the torque axis.


and does that mean that castings are not inferior in tensile fatigue?
idiot.

>
> Those two concepts are basic engineering mechanics. You can
> demonstrate them easily, by bending and twisting a rubber eraser.
> Putting it all together, you should be able to understand that your
> cranks, stem, brake levers, brake arms, seatpost, shift levers,
> handlebars, etc. all undergo tensile fatigue. It's possible to
> successfully design for it.


not if you don't understand where the tensile stresses are you can't!!!
see above. idiot.

>
> But third (and perhaps easiest to understand) is that the specific
> thing jim beam warns about - front mounting of disk brakes - has been
> employed on multi-hundred-pound motorcycles for many decades. The
> direct tensile stresses that come from such mounting are small, and
> very easily accommodated. If they were not, NHTSA and CPSC would have
> told you about it in the recall documents for those motorcycles.


so how much does a motorcycle fork cost frank? and are you saving
weight? if you want to save weight and save money with a casting, you
don't load the material in a way /known/ to be a risk. idiot.

>
> So yes, there's a grain of metallurgical truth in what j.b. says. But
> the design proclamations he derives from it are nonsense. He's making
> a mountain out of a molehill for reasons of his own.


coming from a guy that doesn't understand bending stresses, that's
pretty peachy. idiot.
 
J

jim beam

Guest
[email protected] wrote:
> Ben C? writes:
>
>>>>>>> Placing the caliper in from of the fork would result in the
>>>>>>> reaction force driving the axle into the dropout and
>>>>>>> eliminating the ejection force altogether.

>
>>>>>> Of course true, but although not impossible, undesirable.

>
>>>>> Why is that undesirable?

>
>>>> Because it puts the mounting point in tension as explained by Kim

> beam.
>
>>> Every bending element is subject to tension. Thee is nothing wrong
>>> with tension or we couldn't build anything right from the Golden
>>> Gate Bridge to the elevator next to the stairs. There is nothing
>>> wrong with tension as we see in spokes that don't fail at mid span
>>> where they are entirely in tension. It is unintended bending that
>>> causes most failures and these fail on their tensile side. Don't
>>> give tension a bad name or we can't play tennis or listen to
>>> stringed instruments.

>
>> I think dim beam's point was that this was a tensile fatigue cycle,
>> which tends to be worse than a compressive one, especially for
>> things that are cast.

>
> Fracture occurs on tension but the compression cycle is equally
> important. Obviously the part will not separate on compression but
> its crack propagation takes place. I think this is not the place to
> learn about material science. What is presented may be true and
> correct but the emphasis is often not, so you can get the wrong
> impression.


insufficient understanding of materials is a major factor in failures.
if engineers bothered to understand materials more, the world would be a
much safer place.

>
>>>> Also I am concerned about grit, brake dust etc. coming out of the
>>>> back of the caliper being thrown upwards towards the rider's face.
>>>> With the caliper behind the fork it's directed towards the road
>>>> behind the front wheel.

>
>>> For a particle to fly into your face, it would need to be at least
>>> as large as a grain of coarse sand that flies of the front tire all
>>> the time when on road edge pavement or dirt roads. This is not a
>>> hazard.

>
>> Anyway I got it the wrong way round-- it would be thrown downwards
>> by a front caliper, and upwards by a rear caliper!

>
> I find your preoccupation with the hazards of tension more important
> to resolve.
>
> Jobst Brandt
 
B

Ben C

Guest
On 2007-02-14, [email protected] <[email protected]> wrote:
> Ben C? writes:

[...]
>> I think dim beam's point was that this was a tensile fatigue cycle,
>> which tends to be worse than a compressive one, especially for
>> things that are cast.

>
> Fracture occurs on tension but the compression cycle is equally
> important. Obviously the part will not separate on compression but
> its crack propagation takes place.


I think it's not just that. My understanding is that crack propagation
is predicted to be faster, and fatigue life shorter, if the cycle is
tensile rather than compressive.

A cracked mounting is a failure either way.

> I think this is not the place to learn about material science.


It's better than nothing.

> What is presented may be true and correct but the emphasis is often
> not, so you can get the wrong impression.


I think what jb says is true and correct in this case. The emphasis is
relative-- it's not disastrous to put the caliper on the front, but
neither is it disastrous to put it on the back. See below.

[...]

> I find your preoccupation with the hazards of tension more important
> to resolve.


You may be overestimating my preoccupation with the hazards of tension.
As I've said I don't think a front mounted caliper is impossible, just
that all things being equal, why not take advantage of the improved
fatigue characteristics of putting it behind the fork?

But are all things equal? My own calculations and reasoning (dubious
though they may be...) suggest that with a 2:30 caliper and a 30 degree
forwards exit we have 57 degrees between ejection force direction and
dropout exit direction. The magnitude of the ejection force can be as
big as you like, unless that angle is < 45 degrees, the wheel is not
going to come out of the dropout. In this case I weigh the
(non-existent) risk of ejection lower than the fatigue advantage.

On the bike you tried this on, roughly what were the caliper and dropout
angles?

With unfavourable angles (3:00 and vertical), I'm not so sure. Then you
have to worry about whether the QR strong enough to keep the wheel in
and we've heard all the arguments. IMO you have to consider that lots of
people don't do up the QR properly, so it's risky to count on that.

But finally, as people have pointed out we have only very sparse
evidence that this failure actually occurs.
 
B

Ben C

Guest
On 2007-02-14, [email protected] <[email protected]> wrote:
> On Feb 13, 4:31 pm, Ben C <[email protected]> wrote:
>> I think jim beam's point was that this was a tensile fatigue cycle,
>> which tends to be worse than a compressive one, especially for things
>> that are cast.

[...]
> There are several things you should realize about this. First,
> tension (i.e. tensile fatigue) stresses are present in anything that
> undergoes repeated bending. The tension happens on the outside of the
> bend.
>
> Second, tension (i.e. tensile fatigue) happens in anything that
> undergoes repeated twisting, or torque. In that case, the tension
> tends to be directed at a 45 degree angle to the torque axis.
>
> Those two concepts are basic engineering mechanics. You can
> demonstrate them easily, by bending and twisting a rubber eraser.
> Putting it all together, you should be able to understand that your
> cranks, stem, brake levers, brake arms, seatpost, shift levers,
> handlebars, etc. all undergo tensile fatigue.


I understand those things. Tensile fatigue is not a dragon under the
bed, but neither is wheel ejection. They need to be considered in
proportion to each other.

> It's possible to successfully design for it.
>
> But third (and perhaps easiest to understand) is that the specific
> thing jim beam warns about - front mounting of disk brakes - has been
> employed on multi-hundred-pound motorcycles for many decades. The
> direct tensile stresses that come from such mounting are small, and
> very easily accommodated. If they were not, NHTSA and CPSC would have
> told you about it in the recall documents for those motorcycles.


Noone's disputed that a front caliper is possible, but motorbikes are
not bicycles. All the relative pros and cons are different, which makes
it a different optimization problem and we should not be surprised if it
has a different solution. Lots of motorbikes do have rear calipers
anyway.

> So yes, there's a grain of metallurgical truth in what j.b. says. But
> the design proclamations he derives from it are nonsense. He's making
> a mountain out of a molehill for reasons of his own.


The point is that wheel ejection is a molehill of similar proportions.
 
On 13 Feb 2007 21:43:27 -0800, [email protected] wrote:

>On Feb 13, 4:31 pm, Ben C <[email protected]> wrote:
>>
>>
>> I think jim beam's point was that this was a tensile fatigue cycle,
>> which tends to be worse than a compressive one, especially for things
>> that are cast.

>
>That was jim beam's point, although he takes the phrase "tends to be
>worse" and translates it to "YOU MUST NEVER USE CASTINGS IN TENSILE
>FATIGUE, IDIOT!!" or something like that. ;-)
>


He does do things like that - there was that silliness about how brake
bolts with cut threads were a disaster waiting to happen; he took the
small truth that cut threads are weaker than rolled ones and forgot
the realise that the stresses involved were not large enough that the
difference mattered.

I think he's a teenager who got a beginner book on materials science a
few years ago for christmas, and is trying to tell everyone how smart
it makes him.
 

dabac

Well-Known Member
Sep 16, 2003
2,298
288
83
52
jim beam said:
....the real consideration of course is how great the collapsing force is in
relation to capacity, not whether a collapsing force exists....

But you're completely ignoring the different orders of magnitude of effort needed to address the different issues. Old school risk reduction principles tended to foster a tunnel visioned approach like that.
Sure, wheel ejection is rare and avoidable through known means, and there are other failures that are far more common and equally if not more critical. But are there any who are as easily corrected and with as little impact on the whole concept of bike riding/bike owning as changing dropout angle and/or caliper location(even if it only is to top mount and not forward mount)?

Of course one could, in the interest of safety, require that all bike components should be redesigned with a bigger safety margin and with redundancy on critical systems(2-circuit for hydraulic brakes, double clamps on wire operated etc), but that would have a major impact on just about every aspect on riding, servicing and bike ownership.
Assuming that fork molds gets changed regularly anyhow changing dropout angle and caliper location OTOH makes an admittedly small risk go away w/o any rider consequences.
 
M

Marz

Guest
On Feb 14, 4:48 am, Ben C <[email protected]> wrote:
> On 2007-02-14, [email protected] <[email protected]> wrote:
>
>
>
>
>
> > On Feb 13, 4:31 pm, Ben C <[email protected]> wrote:
> >> I think jim beam's point was that this was a tensile fatigue cycle,
> >> which tends to be worse than a compressive one, especially for things
> >> that are cast.

> [...]
> > There are several things you should realize about this. First,
> > tension (i.e. tensile fatigue) stresses are present in anything that
> > undergoes repeated bending. The tension happens on the outside of the
> > bend.

>
> > Second, tension (i.e. tensile fatigue) happens in anything that
> > undergoes repeated twisting, or torque. In that case, the tension
> > tends to be directed at a 45 degree angle to the torque axis.

>
> > Those two concepts are basic engineering mechanics. You can
> > demonstrate them easily, by bending and twisting a rubber eraser.
> > Putting it all together, you should be able to understand that your
> > cranks, stem, brake levers, brake arms, seatpost, shift levers,
> > handlebars, etc. all undergo tensile fatigue.

>
> I understand those things. Tensile fatigue is not a dragon under the
> bed, but neither is wheel ejection. They need to be considered in
> proportion to each other.
>
> > It's possible to successfully design for it.

>
> > But third (and perhaps easiest to understand) is that the specific
> > thing jim beam warns about - front mounting of disk brakes - has been
> > employed on multi-hundred-pound motorcycles for many decades. The
> > direct tensile stresses that come from such mounting are small, and
> > very easily accommodated. If they were not, NHTSA and CPSC would have
> > told you about it in the recall documents for those motorcycles.

>
> Noone's disputed that a front caliper is possible, but motorbikes are
> not bicycles. All the relative pros and cons are different, which makes
> it a different optimization problem and we should not be surprised if it
> has a different solution. Lots of motorbikes do have rear calipers
> anyway.
>
> > So yes, there's a grain of metallurgical truth in what j.b. says. But
> > the design proclamations he derives from it are nonsense. He's making
> > a mountain out of a molehill for reasons of his own.

>
> The point is that wheel ejection is a molehill of similar proportions.


Exactly. There's some basic math that shows that for a given caliper
position some element of a downward force can act through the drop
out, but in most cases (it seems) a QR can easliy hold the wheel in
place against such a force. If there is enough force to eject a wheel
with a correctly tightened QR, propelling the left handside (because
folks claim that's where all the force acts) of the QR out of the drop
out and over the lawyer lips then the damage to the drop out would be
obvious. Also if this huge force is able to eject one side of a wheel
before the other, shouldn't damage to the QR also be evident.

Can anyone post a picture of a dropout after a disk brake wheel
ejection?

If the QR is loose and the fork and calipers are of a certain design
and you've just ****** off your God, then I can see how a wheel could
be ejected.

Oh and I never 'correctly' tighten my QRs, I use as much force as
possible, but not so I can't open them again without tools.
 
J

jim beam

Guest
dabac wrote:
> jim beam Wrote:
>> ....the real consideration of course is how great the collapsing force
>> is in
>> relation to capacity, not whether a collapsing force exists....

>
> But you're completely ignoring the different orders of magnitude of
> effort needed to address the different issues. Old school risk
> reduction principles tended to foster a tunnel visioned approach like
> that.
> Sure, wheel ejection is rare and avoidable through known means, and
> there are other failures that are far more common and equally if not
> more critical. But are there any who are as easily corrected and with
> as little impact on the whole concept of bike riding/bike owning as
> changing dropout angle and/or caliper location(even if it only is to
> top mount and not forward mount)?
>
> Of course one could, in the interest of safety, require that all bike
> components should be redesigned with a bigger safety margin and with
> redundancy on critical systems(2-circuit for hydraulic brakes, double
> clamps on wire operated etc), but that would have a major impact on
> just about every aspect on riding, servicing and bike ownership.
> Assuming that fork molds gets changed regularly anyhow changing dropout
> angle and caliper location OTOH makes an admittedly small risk go away
> w/o any rider consequences.
>
>

to some extent, and i've said as much before. but q.r. failure, the
biggest issue in all this, will still lead to disaster, angled dropouts
or not. all this chicken little b.s. based on irrational fears created
by bad math, with the biggest adherents being non-engineers that can't
grasp the most basic fundamentals, it beyond bizarre.

focus on the freakin' q.r., that's the safety issue, not the dropouts.
 

dabac

Well-Known Member
Sep 16, 2003
2,298
288
83
52
...
Elsewhere in this thread, I've pointed out that the fellow whose QR
came "completely open" explained that he had just become really
paranoid about the matter. He mentioned no previous QR problems, but
strangely his QR obligingly came undone shortly after he checked it.

So I'm wondering why QR's that apparently never popped open before
people read about the possible danger promptly pop open as soon as
they hear about the problem.

It seems odd to me. Does it seem odd to you?

But there's a significant element of "chicken or the egg" in this - what came first, the phenomenon or the phrase? An event that previously might have been shrugged off as "one of those things", or "sh*t happens" is far more likely to get noticed when someone has defined it and given it a nice label.

Recent medical history offers a couple of examples on how media attention seemingly overnight can increase the number of afflicted considerably, e.g. sensitivity to electro-magnetic radiation, mercury poisoning from dental amalgam and more recently fibromyalgia and chronic fatigue syndrome.

(I'm not trying to be rude to those truly suffering from any of the above, but the media influence is intriguing.)
 
On Feb 14, 12:48 am, jim beam <[email protected]> wrote:
> [email protected] wrote:
> >
> > EP and jb go on about initial conditions not being verified (or some
> > such thing) without ever specifying what they'd accept as a standard
> > for verification. Obviously, the procedures normally used (such as
> > clamp angle of the QR) don't qualify in their eyes.

>
> > They give the impression the only accepted testimony involves QRs
> > tightened with a torque wrench whose resolution is 0.1 inch-pounds.
> > Then checked again at the bottom of a suitable descent. With the
> > entire process done in front of three witnesses. Who sign a document
> > of testimony. Which is notarized.

>
> classic krygowski getting red herringed. torque wrench means nothing
> across different qr's since friction on each is different.


:) That's even better, jim.

Previously, you've implied gaging proper QR installation by clamp
angle, as usually advised (90 degrees, 80 degrees, etc.) isn't valid.
Now you say even the amount of torque applied to the QR can't prove
it's been properly fastened.

In effect, that means there is _no_ practical way of telling if the QR
is clamped properly. That's certainly a handy state of affairs for a
guy who wants to blame all failures on user error!

> all that matters is indention, since that's what generates retention force.


And how is one to gage "indentation"? Release the QR and look for
marks? Obviously, that's testing ex post facto. It does nothing for
a person intending to leave the QR clamped and ride.

This doesn't even treat the fact that you've never specified a
specific depth of indentation. Is 0.010" enough? How about 0.005"?
How about 0.001"? And how will that be measured in the field?

Furthermore, any indentation being examined might be from a previous
installation of the QR, not the current one - which may be adjusted
differently. (In fact, if a deeper previous indentation exists, the
current installation may be tightened on flat surfaces adjacent to
that indentation, but slip into it due to motion induced by impacts.
When that happens, skewer tension _decreases_.)

You've shown your hand. Your standard for disproving user error is
purposely unattainable. Therefore, you will never accept any failure
account as anything but user error. Your bias is total and complete.

- Frank Krygowski
 
On Feb 14, 1:00 am, jim beam <[email protected]> wrote:
> [email protected] wrote:
> >

>
> > So yes, there's a grain of metallurgical truth in what j.b. says. But
> > the design proclamations he derives from it are nonsense. He's making
> > a mountain out of a molehill for reasons of his own.

>
> coming from a guy that doesn't understand bending stresses, that's
> pretty peachy.


:)

When the State Board of Examiners graded my test for the Professional
Engineeer's license, they heartily disagreed with you.

- Frank Krygowski
 
On Feb 14, 3:48 am, Ben C <[email protected]> wrote:
> On 2007-02-14, [email protected] <[email protected]> wrote:
>
> > But third (and perhaps easiest to understand) is that the specific
> > thing jim beam warns about - front mounting of disk brakes - has been
> > employed on multi-hundred-pound motorcycles for many decades. The
> > direct tensile stresses that come from such mounting are small, and
> > very easily accommodated. If they were not, NHTSA and CPSC would have
> > told you about it in the recall documents for those motorcycles.

>
> Noone's disputed that a front caliper is possible, but motorbikes are
> not bicycles.


True. They're much more massive, travel at much higher speeds, and
impose much higher forces on their caliper attachements.

> All the relative pros and cons are different, which makes
> it a different optimization problem and we should not be surprised if it
> has a different solution. Lots of motorbikes do have rear calipers
> anyway.


Do you know of any motorcycle with a rear caliper and a quick release
front axle? I don't believe they exist. Every motorcycle I've owned
or seen had a through-axle. Thus, the hazard imposed by a rear
caliper was removed by other means.

> > So yes, there's a grain of metallurgical truth in what j.b. says. But
> > the design proclamations he derives from it are nonsense. He's making
> > a mountain out of a molehill for reasons of his own.

>
> The point is that wheel ejection is a molehill of similar proportions.


If you want to prove the front-mount-fatigue issue is of similar
importance to the bike wheel ejection issue, it should be easy for you
to do so. Just post here the tales of motorcycles losing their front
mount calipers due to fatigue. Carl has posted several examples of
candidate motorcycles to check. If you find enough such tales, I'll
believe the hazards are similar.

My claim is that the fatigue hazard is entirely jim beam's invention.
You have an opportunity to prove me wrong.

- Frank Krygowski
 
B

Ben C

Guest
On 2007-02-14, [email protected] <[email protected]> wrote:
> On Feb 14, 3:48 am, Ben C <[email protected]> wrote:

[...]
>> The point is that wheel ejection is a molehill of similar proportions.

>
> If you want to prove the front-mount-fatigue issue is of similar
> importance to the bike wheel ejection issue, it should be easy for you
> to do so. Just post here the tales of motorcycles losing their front
> mount calipers due to fatigue.


If no such tales can be found that just proves that the motorcycle
designers made sufficiently strong or fatigue-resistant caliper mounts
to overcome the problem. I would expect the likes of Honda to get that
right whatever the basic design. It doesn't tell us anything about the
relative importances of fatigue and ejection.

> My claim is that the fatigue hazard is entirely jim beam's invention.


Yes, I also give jim beam the credit for pointing out the fatigue
hazard.
 
E

Ed Pirrero

Guest
On Feb 13, 9:20 pm, [email protected] wrote:
> On Feb 13, 9:17 pm, "G.T." <[email protected]> wrote:
>
>
>
> > EP, jb, and CF clearly don't trust Annan, Missy Giove, Dave Smith, Russ
> > Pinder, and I doubt they'll trust anyone else who claims they checked their
> > QRs before the QRs magically loosen.

>
> I think this is true...


Then you think wrong. Just like GT. You bring this up every time
this discussion occurs, as a handy device to dismiss any questions
about what could be baseless assumptions on your part.


> EP and jb go on about initial conditions not being verified (or some
> such thing) without ever specifying what they'd accept as a standard
> for verification.


I'd like to see SOME sort of second opinion. For anyone who's ever
ridden off, only to look down and see the QR loose (disk brake or
not), knows exactly what I'm talking about. Certainly that wasn't
done on *purpose*, so that person obviously thought they had done it
up, and done it up correctly.

So the question really becomes - how did these folks' stories become
data?


> Obviously, the procedures normally used (such as
> clamp angle of the QR) don't qualify in their eyes.


Hooray! Another strawman.

> They give the impression the only accepted testimony involves QRs
> tightened with a torque wrench whose resolution is 0.1 inch-pounds.
> Then checked again at the bottom of a suitable descent. With the
> entire process done in front of three witnesses. Who sign a document
> of testimony. Which is notarized.


:roll eyes:


Yeah, Frank - that MUST be true. Ooops, it isn't. But keep repeating
the same lie, and pretty soon it'll become true, right?

I'll repeat it again, since you and G.T. can't seem to get it the
first eight or twevle times I've said it: Nobody, no you, not me,
*nobody* - knows the initial conditions with certainty. You make the
assumption that the initial conditions are as reported, and I don't.
Another difference between us is that I am completely willing to admit
the conditions are as-reported. You, OTOH, are not willing to admit
that the users of this equipment might be human and might have made an
error.

I doubt you have the intellectual honesty to stop misrepresenting my
position on this issue, but one can hope for a first time...

E.P.

> I think everyone accepts that most QRs hold most front disk axles in
> place most of the time. IOW, the set of conditions generating
> loosening and ejection is uncommon, and some of the conditions may not
> be known. It's foolish to expect a stellar verification team to
> happen to be present at the top of a particular hill just before all
> conditions are right to cause loosening or ejection.
>
> Unless, that is, someone purposely sets up a demonstration just to
> convince them. But to go through that trouble, one would have to
> pretend their opinions actually mattered, and the concensus here seems
> to disagree.
>
> - Frank Krygowski
 
E

Ed Pirrero

Guest
On Feb 13, 6:17 pm, "G.T." <[email protected]> wrote:
> "Tim McNamara" <[email protected]> wrote in message
>
> news:[email protected]
>
> > In article <[email protected]>,
> > "Ed Pirrero" <[email protected]> wrote:

>
> >> On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:

>
> >> > It's sad that you and jb are such untrusting fools.

>
> >> Logical fallacy - ad hominem.

>
> > That's a correct call.

>
> "Fools" may be ad hominem but the untrusting part is not a logical fallacy.


Science is not about faith, Greg. So, let me ask you this: is it
possible, even slightly, that any or all of these incidents are due to
user error? It's a yes/no question.

I think everybody already knows the answer. The question really is:
are you intellectually honest enough to give that answer?

E.P.
 
G

G.T.

Guest
Ed Pirrero wrote:
> On Feb 13, 6:17 pm, "G.T." <[email protected]> wrote:
>> "Tim McNamara" <[email protected]> wrote in message
>>
>> news:[email protected]
>>
>>> In article <[email protected]>,
>>> "Ed Pirrero" <[email protected]> wrote:
>>>> On Feb 12, 3:49 pm, "G.T." <[email protected]> wrote:
>>>>> It's sad that you and jb are such untrusting fools.
>>>> Logical fallacy - ad hominem.
>>> That's a correct call.

>> "Fools" may be ad hominem but the untrusting part is not a logical fallacy.

>
> Science is not about faith, Greg. So, let me ask you this: is it
> possible, even slightly, that any or all of these incidents are due to
> user error? It's a yes/no question.
>


Of course. But there's nothing I've read of yours that admits it could
be possible, even slightly, that any or all of these incidents are due
to poor design.

Greg

--
"All my time I spent in heaven
Revelries of dance and wine
Waking to the sound of laughter
Up I'd rise and kiss the sky" - The Mekons